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Topic: Multidisplay, a Open Source inCar Display, Logger (Read 104434 times) previous topic - next topic


Looks cool Designer2k2!

I've been fighting with this LM2917N... its sticking out a reference voltage of 1.2V and then seems to work best actually triggering on a GND than a VCC  :-/ So I've got something screwy in my circuit im trying to sort out ...

Checkout my projects development blog @ SLiDA


do you have a special reason for the LM2917 in the 14pin case?

one difference is that on the 14pin you need to shortcut pin 3 and 4 directly, look at the 8pin where its internaly connectet.
in your circuit you have pin 3 with a C and pin 4 with an R to ground.

same for pin 11 and 12, they are internaly shortcuttet and then routet to ground, you have a R6/D2 there.

and pin 8, 9 i have also shortcuttet, you used R7. but that looks ok becouse of the zener.

something like this should be a copy from the 8pin to the 14pin:

i thing its right like this, but its sunday after a short night  :D


Aug 16, 2009, 08:51 am Last Edit: Aug 16, 2009, 08:52 am by adr1an Reason: 1
No special reason other than thats my local availability and so thats all I could get 'off-the-shelf'.. I would have been better off getting an 8-pin in from futurelec in hindsight....

Thanks for the circuit - i did pickup my lack of bridge on 3/4.. i'll have a fiddle based on the schematic you kindly provided shortly..
Checkout my projects development blog @ SLiDA


got the interface nearly assembled:

im very happy how well the 2 layers align, but making the vias is a sh*** job  :P

and put my prototype in the car:

i messed up the video  :-[ , but its working  :D

drove about 2 hours arround, the LCD sometimes shows crap (need to make it more stable) but even as i had 43°C in the car it worked perfect :)


Looking good!

Is the SuperCap on the PCB to survive cranking/start-up ?
Checkout my projects development blog @ SLiDA


to survive starting i have a big cap in the power supply, the one on the interface should get me a stable 5V for the ADW´s.

this print will be connected with a 2-3m network cable to the arduino, and located in the engine bay. im hoping that the big cap is enough to remove noise   :-/


Aug 19, 2009, 06:25 pm Last Edit: Aug 20, 2009, 11:30 am by adr1an Reason: 1
Ok.. Im about to start abusing things. I've breadboarded this, and I've made the changes as per your suggested schematic and I'm going insane. Can't get it to work properly at all.

I am going to leave it for the moment.. I think the fact I'm using a tantalum instead of a ceramic for the 2 x 1µF Caps isn't helping.. I'll pickup some Monolithics tomorrow..

Im not convinced I've got the 2917N pinned right either... its just not behaving properly at all. Guess my caps aren't helping... but if I have the lower board connected to ground I get nothing much.. if I leave the bottom ground floating I get voltage - now thats just all whacked to start with :( Then if I bridge the ground I can only manage about 0.6V's out the other side. I've even gone back to using a 130K resistor in place of the trimpot, so it should be identical to your setup..

Heres a pic in case you can spot anything obvious... Yellow jumpers are the input frequency, white jumpers are the RC circuit, Blue is the signal out, red and black are pwr and ground... the LED is hooked up to the signal out wire just to give me a visual reference...

a full res version is at http://slida.canberrariders.org.au/wp-content/uploads/2009/08/P1040265.JPG

This is really annoying me now :( If only I had a damn 8-pin 2907.... Argh!!!! Im pretty sure I need to do some more work on the 2917.. you'll see on this tach schematic that 11 is pulling off of the supply as well.. I think 11 is important to the Internal Zener? I dunno.. Im too tired right now to work it out .. all the example apps seem to hook it between VCC with a pullup and GND with a sig-diode......

EDIT: Ok, picked up some 1µF Monolithic Ceramics today, so am replacing the tantalums. Don't ask  :-? . After that, I'll modify my circuit to have the signal diode and 10K pull up off of pin 11 - it seems to be constant across the few 2917 examples I could find. Wish me luck.  ;D
Checkout my projects development blog @ SLiDA


on a first view the breadboard does seem right, but its tricky to see everything  :-/

order a 2907 in 8pin, i think thats the easier way instead off debugging this...


Yeah... Im chasing down an 8-pin.. but damn it .. I refuse to admit defeat!! :)

I think I need to ditch the BC557 and look at my pinout again.. w/ the 2917N I dont need an AC input.. it can be just a DC differential...

I'm *really* sucking at this effort... and I dont know why... it should be a fairly simple circuit  :o
Checkout my projects development blog @ SLiDA


i would understand it different...

my input to the circuit ist a switched 12V, no AC. The BC557 just helps to get a nicer signal into the LM, you need some sort of other circuit then becouse having a 5V supply but giving a 12V input doesnt work  ;)

from your Applications Information i take that the LM2917 is needed when the supply voltage is not stable, but we have nice 5V?

Basically yes, just giving it up is not good, but you could get a lm2907 to work, and have something what works, and then chase the 2917 problem. But you removed the show-stopper  ;)


got them prints ready and ordered 1 to see how they look when they are professional made :)

the arduino main print:

the interface print for all the sensors:

More information including the schematics: http://code.google.com/p/multidisplay/wiki/SplitBox


the main print is here  :D

my first ever ordered professional print. glad it worked so well, hope it will work as nice as it looks  8-)


Oct 15, 2009, 09:23 pm Last Edit: Oct 15, 2009, 09:24 pm by designer2k2 Reason: 1
Started to build the first kit:

today i made the main print, where the Arduino, LCD and powersupply is:

the breadboard version:

and the real thing:

and it works:


tomorrow i build the sensorprint (shown above in my selfmade version) and then its very close to get into my car  8-)


the first Kit is build and running:

Check the Website for more informations: http://code.google.com/p/multidisplay/


updated the SVN, Partlists, Layouts and the Wiki, everything you need to make one off this is now online  :)

wiki: http://code.google.com/p/multidisplay/

Instructions: http://code.google.com/p/multidisplay/wiki/Build_a_Kit

when running like planned i will install the first kit this weekend  8-)

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